Unfortunately there is no social group function in the apps. Probably in next year's version but I can't give you an exact date.
To get to groups in the old mobile skin, go to http://www.bubhub.com.au/mobile2009, click 'user control panel' then 'groups.' The groups are displayed in a modern format so it may be too much for some older phones.
The modern mobile version doesn't have groups enabled at this stage.
PS we're currently working on the mobile skins so you may not be able to use them right now.